How can I send users to a custom page when they check out?

I have a potential product that I want to test by setting up a store to "sell" it. I want users to be able to go through the checkout process, but at the end be sent to a page that says something like "This product is on back order. Your credit card has not been charged." and obviously not actually charge them or store any payment info. Just record one hypothetical "sale". Is there a way to do this with squarespace?